This invention relates to apparatus for mixing water with CO.sub.2 gas to produce carbonated water in a storage tank and operates to cool its contents and to form an ice bank adjacent the cooling pipes of a cooling circuit in the wall area of the storage tank, whose interior also includes the placement of a circulating pump, whereby CO.sub.2 gas from the head area of the storage tank is mixed by rotation and/or circulation with the water inside the storage tank. Both fresh water and CO.sub.2 gas are fed into the head area of the storage tank while carbonated water is removed from the base or bottom of the tank.
Apparatus which mixes water with CO.sub.2 gas to produce carbonated water is well known and is used, for example, in post-mix beverage dispensing machines so that carbonated beverages can be prepared and dispensed on demand by mixing carbonated water with a suitable drink concentrate. The carbonated water mixed with the drink concentrate is produced directly in the storage tank by mixing water and CO.sub.2 gas which is fed thereto and thereafter cooled for better carbonation, this being a requirement for a cool refreshing drink which is prepared for consumption as the need arises. The storage tank, commonly referred to as a carbonator, is fed fresh water of drinking quality either from the line of a water supply system or a pressurized storage tank. The fresh water, moreover, can be fed from the water supply system under pressure and can be enhanced, when desired, by the use of a pressure pump. Further, CO.sub.2 gas is fed to the carbonator from a CO.sub.2 gas storage tank by a pressure-reducing regulating valve so that a pressure of, for example, about 4 bars is built up in the carbonator.
In order to ensure sufficient carbonation of the fresh water, the carbonation process can be accomplished by or assisted by the use of a CO.sub.2 circulating pump located in the carbonator. This type of pump draws CO.sub.2 gas from the upper or head-space region of the carbonator filled with CO.sub.2 gas and blends it with circulating water which is set in circular motion, such as by spinning.
As already noted, cooling of the carbonator is used, not only to improve the carbonation, but also as a requirement so that the finally prepared and dispensed drink exhibits a desired low and basically constant temperature. The cooling of the carbonator is achieved by a cooling system, which is adapted to form an ice bank of generally uniform thickness along the inner side walls of the carbonator as a result of the circulating water. Consequently, a cooling capacitor is produced, thus enhancing its "refrigerating capacity", thereby removing the need for a relatively powerful cooling system which would be necessary in a once-through cooling system.
In the dispensing of a freshly prepared carbonated drink, a shutoff valve is typically opened in a line connected to the bottom of the carbonator, whereupon cooled carbonated water is fed therefrom to a concentrate mixing station. As a result of forming the ice bank in the area of the cooling coils, the carbonated water is cooled to near the freezing point.
Arrangements having a corresponding design as described above are well known, a typical example being shown and described in U.S. Pat. No. 5,184,942, Deininger et al, Feb. 9, 1993.
Apparatus of the type described above is designed for normal use and typical operating conditions. These conditions include not only its inherent operating characteristics, but also its intended operating environment. Thus, one assumes that household equipment is used in settings where standard temperature conditions are encountered. For cooling equipment, including not only refrigerators and freezers, but also cooling apparatus for post-mix carbonated beverage dispensers, external temperature conditions, however, can be of great importance due to the fact that performance efficiency of the cooling system declines as a function of the increase of the temperature difference between the area to be cooled and the immediate surroundings. The converse is also true.
Accordingly, cooling systems are normally designed so that even with relatively high ambient temperatures, sufficient cooling can be provided for its intended use. However, since such cooling systems are also used at relatively low ambient temperatures, their output capacity is usually compensated for by factors which results in over design of the equipment. This fact per se appears to be rather harmless. However, in the case of carbonator storage tanks for preparing and then storing carbonating water for subsequent use in a post-mix dispenser, cooling coils of a cooling circuit used to cool the water are located in the wall area of the tank. In such apparatus, it has been observed that any significant temperature reduction relative to normal room temperatures can produce disadvantageous results. These drawbacks can be overcome, partially at least, not only by the inertia of the refrigeration system, but also by the reduced heat conductivity of the ice in the ice bank typically formed inside the tank adjacent the cooling coils.
Although the thickness of the ice bank is monitored by means of an ice sensor which controls the refrigeration cycle, the ice bank tends to become thicker when the outside or ambient temperature drops. This has been found to lead to undesirable consequences such as malfunctions inside the carbonating water storage tank.